Biological Molecules

Biological Molecules

  • Biological molecules are the vital substances found in living organisms, helping in growth, development, and functioning of life processes.


  • Carbohydrates are essential biological molecules that majorly serve as an energy source.
  • Chemically, they are comprised of carbon, hydrogen, and oxygen.
  • They can be simple, including monosaccharides like glucose, or complex, such as polysaccharides like starch.


  • Lipids are biological molecules which are hydrophobic or insoluble in water.
  • They include fats, oils, and cholesterol.
  • Lipids play important roles in long-term energy storage, insulation, and cell membrane formation.


  • Proteins are large biological molecules made up of one or more chains of amino acids.
  • These are required for the structure, function, and regulation of body’s tissues and organs.
  • Proteins, such as enzymes and antibodies, perform a vast array of functions within organisms.

Nucleic Acids

  • Nucleic acids, such as DNA and RNA, are complex organic substances present in living cells.
  • They are responsible for the storage, transmission, and execution of genetic information.
  • DNA is the molecule that holds the instructions for all living things, while RNA is involved in protein synthesis.

Testing for Biological Molecules

  • Biological molecule tests help in determining the presence of specific molecules in a sample.
  • A positive starch test will turn the iodine solution blue-black.
  • Benedict’s test for reducing sugars results in a color change from blue to green, yellow, or brick-red on heating.
  • The biuret test for proteins turns the solution lilac or purple.
  • The paper test for lipids leaves a translucent spot on the paper.